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Relocating batteries

The house battery bank was quite old and placed in the bilge, which we didn't like. I started by removing the old batteries from the bilge and cleaning the area. Unfortunately the structural members were also cut out to be able to fit the batteries there, so we're planning to reinforce them later this year.

Old batteries in the bilge

The previous owner left us two uninstalled 200 Ah AGM batteries which he claimed to be almost new. We were hoping to install them and trying hard to find an adequate place for those big and heavy batteries. But before making the decision and starting the work, we decided to buy a battery analyzer and check if they're really in a good condition and worth to install. It turned out to be a good idea. The batteries are unfortunately almost dead and needs to be replaced. It's bad and good news at the same time. Bad because batteries are expensive to replace and good because now we can be more flexible with the size, capacity and placement.

Battery tester

I got three new 100Ah deep-cycle Marin AGM batteries, RitarPower's RA12-100 as they claim it's suitable for deep cycle use, recommended also in UPS/EPS, medical equipment, emergency light and security system applications, and have a 10 years design life in float service. I also considered Mastervolt's MX-series, which is a bit cheaper, but according to Mastervolt, it has a much shorter (3-5 years) design life.

Not sure if the Ritar will last that long, but if we can get 1-2 years extra out of them, it's worth the price difference. After a long hesitation I decided to place the house bank in the aft cabin, right next to the engine room bulkhead. The starter battery will reside on the other side of the bulkhead, in the engine room, behind the steering rod, were it was placed by the factory originally.

The storage area in the aft cabin is just large enough to accommodate the three 100Ah batteries. The steering rod is going through this area, so I also checked if the movement of the rod wouldn't reach the batteries.

Battery location plan

I placed them so that there is still plenty of room between the steering system and the batteries when the rod is at it's closest to starboard. I made a shelf of plywood based on a cardboard template and test fitted it. Looks promising so far. The next step is to fix the batteries in place and connect everything, replacing all the cables and connections that needs to be replaced.

Update from 2022: We decided to move them once again, to the saloon, to give space for a below deck autopilot in the aft locker.